Wet cleaning apparatus utilizing ultra-pure water rinse liquid with hydrogen gas

ABSTRACT

A wet cleaning apparatus can remove trace heavy metals, colloidal matter or other impurities contained in ultra-pure water to be used as rinse water in semiconductor cleaning processes and suppress deposit of trace impurities such as heavy metals or other particles that would otherwise cause characteristics of such devices to deteriorate. A wet cleaning apparatus for rinsing with ultra-pure water as a rinse liquid by supplying ultra-pure water through a piping to a rinse location inside the apparatus. The rinse location is a point of use of the ultra-pure water. The wet cleaning apparatus includes a module filled with porous film in which polymer chains having at least one of an anion exchange group, a cation exchange group, and a chelating group are held in the middle of the piping positioned inside the apparatus. The wet cleaning apparatus further includes a means for adding hydrogen gas to the rinse liquid.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention concerns a cleaner using ultra-pure water, andparticularly a cleaner for use in the wet cleaning process for thesemiconductor industry.

2. Discussion of the Related Art

It has been devised to introduce, just before the point of use, an ionabsorption film module filled with a porous film of 0.01 to 1 μm inaverage hole diameter, the porous film holding polymer chains having acation exchange group, an anion exchange group and a chelating group(hereafter, called cation absorption film, anion absorption film andchelate film, respectively); and each such film being generically calledan ion absorption film for reducing impurities such as heavy metals, forexample, just before the point of use (Japanese Patent Laid-Open No. HEI8-89954).

A hollow yarn film module having a cation exchange group associatedtherewith is applied to eliminate metals, and it is particularlyeffective in eliminating alkali metals and/or alkali earth metals. Ahollow yarn film module having an anion exchange group can effectivelyeliminate particles and colloidal matter. A hollow yarn film modulehaving a chelating group has an excellent function of eliminating heavymetal material, even when present at an extremely low concentration.

It is known that the use of hydrogenated ultra-pure water can suppressand/or eliminate deposition onto a substance of silicon or the like.Further, Japanese Patent Laid-Open No. HEI 9-10713 discloses a methodincluding the steps of presenting an extremely high hydrocarbonelimination rate and by treating the wafer with ultra-pure water inorder to perform substrate hydrogen termination, the ultra-pure watercontaining hydrogen or a mixture of hydrogen and a rare gas. Ashydrogenated ultra-pure water presents an extremely high hydrocarbonelimination rate, using a rinse of hydrogenated ultra-pure water shouldallow a cleaner wafer surface to be obtained than possibly achievedusing a rinse not employing hydrogenated ultra-pure water.

However, through the comparison between a film (for example, aninsulation film such as a gate insulation film) formed on the siliconsubstrate when hydrogenated ultra-pure water is used to rinse and a filmformed on the substrate when non-hydrogenated ultra-pure water is usedto rinse, the Inventors have found a problem that the former filmhappens to be inferior to the latter film in quality (for example,dielectric strength).

They have investigated the cause thereof and have found that thehydrogenated ultra-pure water is capable of eliminating particles and/orof preventing particles from depositing on a substrate, but also has afunction of facilitating deposition of metallic impurities onto thesubstrate. They have explicated that this deposition provokes filmquality degeneration (for example, deterioration of dielectricstrength).

SUMMARY OF THE INVENTION

The present invention provides a wet cleaning apparatus for eliminatinga trace heavy metal, colloidal matter, and/or other impurities containedin ultra-pure water used as rinse water in the semiconductor cleaningprocess and suppressing deposition of impurities, such as particlesand/or heavy metals that degenerate device characteristics, onto thesubstance surface.

According to the present invention, a wet cleaning apparatus for rinsingwith ultra-pure water includes a piping through which is supplied to apoint of use inside the apparatus, the piping being provided with amodule filled with a porous film in which polymer chains having at leastone of a cation exchange group, an anion exchange group and a chelatinggroup held within the polymer chains, the porous film being positionedin the middle of the piping.

Here, the cleaner is a multi-tank type, a single tank type batchcleaner, or a sheet cleaner for performing wet cleaning. In wetcleaning, the cleaner is an apparatus for cleaning a wafer surface withultra-pure water-based chemicals, for rinsing surface chemical depositstherefrom with the ultra-pure water and eventually for drying the wafersurface. Note that such an apparatus includes a cleaner for cleaning byultra-pure water jet.

Here, the cleaner includes a wet bench. A wet bench is a cleaning placeprovided with exhaust equipment and cleaning equipment. The cleaningequipment is provided with ultra-pure water, chemical supply piping, anddrain piping for cleaning liquid and rinse water.

Ultra-pure water produced by the ultra-pure water system alwayscirculates within the main loop and is extracted as necessary from themain loop by means of a branch piping to dilute chemicals necessary forcleaning or rinsing, as appropriate.

Branch piping is introduced into the cleaner or wet bench to supplyultra-pure water for individual cleaning processes, and among them, inthe final rinse corresponding to the final process of the cleaningprocesses, it is an object to eliminate any chemical deposit from thesemiconductor substrate that would otherwise exist thereon aftercleaning.

Here, the final rinse designates the process for rinsing a chemicaldeposit on the wafer surface with ultra-pure water or hydrogenatedultra-pure water just before a wafer drying process, such as IPA(2-propanol) vapor drying, spin drying, or Marangoni-type drying.

As the rinse with ultra-pure water itself does not present an effect tosuppress deposition of impurities such as various types of metal,rinsing water after chemical cleaning should be free from even a traceof impurities.

Especially, in the last process of wet cleaning, the substrate surfaceis etched with dilute hydrofluoric acid solution, a bare siliconsurface, deprived of an oxide film, is exposed, and thereafter, therinse process is performed with ultra-pure water.

There, the object of ultra-pure water rinse is to eliminate hydrofluoricacid chemical deposited on the substrate by rinsing with ultra-purewater. However, if impurities such as metals exist in the ultra-purewater, the use thereof can result in impurity deposition since thesilicon surface is exposed. Once impurities deposit onto the substrate,the ultra-pure water is totally incapable of eliminating them.Consequently, the ultra-pure water used for the final rinse is requiredto be totally free from impurities such as metals that tend to depositonto the substrate surface.

Among impurities present in the ultra-pure water, especially metals, arereduced and hardly detected, even by means of a high sensitivityinstrument analyzer such as an inductively coupled plasma analyzer(ICP-MS).

It is presumed that the presence of impurities under the analyzerquantification lower limit level provokes the deposition of impuritiesonto the substrate surface.

Almost all metals existing in the ultra-pure water are generallyanionized. However, it is presumed that they do not exist as independentanions, but they are clustered or colloidalized, formingelectrostatically weak binding with silica or organic matter havingnegative charge. For this reason, it is difficult to remove theclustered matter having weak charge and small size with ion exchange orreverse osmosis equipment designed to remove metal impurities in theultra-pure water system. It has been found that these metal impuritiesare present at the exit of ultra-pure water system and may deposit ontothe substrate surface.

Here, the investigation by the Inventors has shown that the use of amodule filled with an ion absorption film holding polymer chains havingat least have of a exchange group, an anion exchange group and achelating group can eliminate impurities, such as a clustered metal,that could not be removed by the conventional system.

Here, as the ion absorption film used in the present invention, forexample, a hollow yarn porous film of 0.01 to 1 μm in average holediameter is used preferably, the porous film containing polymer chainshaving ion exchange groups inside the film, the ion exchange groupsforming 0.2 to 10 mili-equivalent weight per 1 gram of film. Themanufacturing method and other details thereof are as described in thedocument JAPANESE PATENT LAID-OPEN NO. HEI 8-89954.

As for ion absorption film, for example, it concerns one havingquaternary anime as an exchange group, and quaternarized chloromethylstyrene is generally used. However, those obtained by quaternarizingazote atoms of pyridine-based or imidazole-based heterocyclic rings canalso be used.

As for a potential cation absorption film, a sulfonic group, phosphoricgroup, carboxylic group or the like are advantageously used as theexchange group.

Concerning a usable chelating group, an iminodi acetic group, mercaptogroup, ethylene diamine or the like can be used as the exchange group.

As a wet cleaning method in the semiconductor production, a cleaningmethod called RCA cleaning, shown in FIG. 1, has been usedconventionally. This RCA cleaning is characterized by blending acid oralkali on the base of hydrogen peroxide, and cleaning at a hightemperature, and repeating ultra-pure water rinsing following chemicalcleaning.

The role of ultra-pure water rinse is nothing other than the removal ofused chemicals from the substrate. However, as the rinse process hardlyremoves impurities other than the chemical solution, it is required tosupply cleaned ultra-pure water. Especially, if the contamination occursin the final rinse, all cleaning processes should be performed overagain. Consequently, it is necessary to take some measures againstrecontamination.

In order to improve the quality of ultra-pure used for a final rinse,the problem of ineffective cleaning in the wet cleaning can be resolvedby integrating these ion absorption film modules into the ultra-purewater piping for final rinse in a cleaner.

In a cleaner according to the present invention, ultra-pure water isfirst treated by a module filled with ion absorption film holdingpolymer chains having at least one of a cation exchange group. An anionexchange group and a chelating exchange group acting as an exchangegroup inside the film when hydrogenated ultra-pure water is used in therinse process of wet cleaning, and then hydrogenated, for instance, whena silicon wafer is to be washed for semiconductor manufacturing.

Hydrogenated ultra-pure water is capable of eliminating particlesdeposit from a substrate and has an effect to prevent particles fromdepositing on the substrate, but when metallic impurities are present,it facilitates disadvantageously the deposition of such metallicimpurities onto the substrate.

It was found that metal deposition onto the substrate can be suppressedeven if hydrogenated ultra-pure water is used, provided that metalimpurities present in the ultra-pure water can be reduced sufficiently.

Consequently, according to the present invention, the deposition of notonly particles but also metal impurities can be suppressed. Besides, aninsulation film having, for instance, a high dielectric strength can beformed on the substrate even when the final rinse is performed by thewet cleaning apparatus of the present invention.

Therefore, a cleaning method wherein ultra-pure water is hydrogenatedafter having sufficiently reduced metal impurities in the ultra-purewater through the treatment with a module filled with ion absorptionfilms and a cleaner capable of carrying out that cleaning method havebeen invented.

Moreover, the ultra-pure water is first hydrogenated when hydrogenatedultra-pure water is used in the rinse process of wet cleaning and thentreated by a module filled with an ion absorption film holding polymerchains having at least one of a cation exchange group, an anion exchangegroup and a chelating group as an exchange group inside the film, when asilicon wafer is to be washed for semiconductor manufacturing.

A combination of any two or more modules filled with an ion absorptionfilm holding polymer chains having at least one of cation exchangegroup, an anion exchange group and a chelating group can be used in thecleaner or wet bench, when a silicon wafer is to be washed forsemiconductor manufacturing.

As for the metal present in the ultra-pure water, though the metalitself is ionized and becomes cationic, matter like negatively chargedsilica or organic acid approaches around the metal, clusters and existsin a colloidal state.

As charge deviation varies according to the nature of the metal elementpaired with silica or organic matter, a complete removal may not beassured by a single film module. However, in such a case, the metal canbe eliminated completely by combining films whereby different exchangegroups are introduced. As a possible combination in one method, twokinds of films can be combined as follows:

Cation absorption film+anion absorption film;

Chelate film+anion absorption film;

Anion absorption film+cation absorption film;

Anion absorption film+chelate film;

Cation absorption film+chelate film; and

Chelate film+cation absorption film

and, in another method, three kinds of films can be combined as follows:

Cation absorption film+chelate film+anion absorption film;

Chelate film+cation absorption film+anion absorption film;

Cation absorption film+anion absorption film+chelate film;

Anion absorption film+cation absorption film+chelate film;

Anion absorption film+chelate film+cation absorption film; and

Chelate film+anion absorption film+cation absorption film. However, thecombination preferably includes a chelate film to eliminate impurities.

Ultra-pure water hydrogenation can take place either upstream of themodule or downstream of the module. If it is performed upstream, themetal deposition onto the substrate can be prevented more effectively.Note that the hydrogenated ultrapure water includes water hydrogenatedfrom exterior and one containing hydrogen from the beginning of themanufacturing.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a process diagram showing the cleaning procedure of thepresent invention;

FIG. 2 is a schematic diagram showing a cleaning system used in Example1;

FIG. 3 is a schematic diagram showing a cleaning system used in Example4;

FIG. 4 is a schematic diagram showing a cleaning system used in Example10; and

FIG. 5 is a schematic diagram showing a cleaning system used in Example15.

NOTIFICATION OF SYMBOLS

1,2,3,4,5 Cleaning tank

6 Ozone generator

7 Ultra-pure water piping

8 Mixing tank

9 Mixing tank

10,12 Fluoric acid weighing tank

11 Hydrogen weighing tank

13 Piping

19 Hydrogen dissolution film module

20,21,22 Ion absorption module

DETAILED DESCRIPTION OF THE INVENTION

In the examples, an anion absorption film, a cation absorption filmand/or a chelate film are used as the ion absorption film. These ionabsorption films are prepared according to the method described in T.Hori et al., Journal of Membrane Science 132 (1997) 203 211.

An anion absorption film has a structure wherein a polymer chain isobtained by introducing a strong basic quaternary ammonium-type ionexchange group into a copolymer of chloromethyl styrene, and divinylbenzene is fixed onto the hollow yard porous film surface.

A cation absorption film has a structure wherein a polymer chain isobtained by introducing a strong sulfonic acid-type ion exchange groupinto a copolymer of styrene, and divinyl benzene is fixed onto thehollow yarn porous film surface.

A chelate film has a structure wherein a polymer chain is obtained byintroducing an iminodi acetic group into a copolymer of glycidylmethacrylate, and divinyl benzene is fixed onto the hollow yarn porousfilm surface.

EXAMPLE 1

FIG. 2 shows a cleaner for performing ambient temperature wet cleaning,accommodating five steps and thereby having cleaning tanks 1 to 5 in thecleaning machine.

Cleaning with ozone ultra-pure water is performed in cleaning tank 1,and megasonic irradiation cleaning is performed by adding surfactant toa fluoric acid-hydrogen peroxide mixture solution in cleaning tank 2.

Cleaning is performed with ozone ultra-pure water in cleaning tank 3,dilute fluoric acid treatment in cleaning tank 4, and a final ultra-purewater rinse in cleaning tank 5.

Cleaning tank 1 and cleaning tank 3 are supplied with ultra-pure waterfrom an ultra-pure water piping 7. Ozone generated by an ozone generator6 and ozone supplied from a piping 13 are mixed and dissolved in theultra-pure water piping 7 and supplied into cleaning tank 1,3 as ozoneultra-pure water.

A mixing tank 8 is installed in association with cleaning tank 2, andmixing tank 8 is suitably supplied with necessary chemicals from aweighing tank 10 of fluoric acid-containing surfactant and from aweighing tank 11 of hydrogen peroxide, and when mixing is finished, thechemicals are transported from mixing tank 8 to cleaning tank 2.

A mixing tank 9 is installed relative to cleaning tank 4, and mixingtank 9 is suitably supplied with the necessary chemicals from a weighingtank 12 of fluoric acid, and when mixing is finished, the chemicals aretransported from mixing tank 9 to cleaning tank 4.

Cleaning tank 5 (i.e., point of use in final rinse) is supplied withultra-pure water from ultra-pure water piping 7, and the dissolvedoxygen concentration of this ultra-pure water was 2 μg/L.

An anion absorption film module is introduced, as ion absorption filmmodule 20, between a supply outlet to cleaning tank 5, and 0.1 μmparticle elimination membrane filter 21 in a branch piping 7 inside acleaning machine, supplying cleaning tank 5 with ultra-pure water, allthe ultra-pure water being filtered by module 20 before introductioninto cleaning tank 5.

First, cleaning with ozone ultra-pure water in cleaning tank 1 throughcleaning with dilute fluoric acid in cleaning tank 4 is performed on asilicon wafer (prepared by a taking up method) of 8 inches in diameter(cz), having an n-type crystal face (100) and a resistivity of 8 to 12Ω·cm. Next, the cleaning is performed by changing the rinse time withthe ultra-pure water in cleaning tank 5 from 10 minutes, 1 day, 3 days,to 7 days. After rinsing, the silicon wafer is dried, and the quantityof metal impurities such as copper, iron or nickel, among the depositedimpurities, is measured by a total reflection X-ray spectrometer, theresults thereof being shown in Table 1.

EXAMPLE 2

In the same cleaner as Example 1, a cation absorption film module isintroduced, as ion absorption film module 20, between the supply outletto tank 5 and 0.1 μm particle elimination membrane filter 21 in branchpiping 7 inside cleaning machine, supplying cleaning tank 5 withultra-pure water, all the ultra-pure water being filtered by module 20before introduction into cleaning tank 5.

First, cleaning with ozone ultra-pure water in cleaning tank 1 throughcleaning with dilute fluoric acid in cleaning tank 4 is performed upon a8 inch, n-type (100), 8 to 12 Ω·cm silicon wafer. Next, the cleaning isperformed by changing the rinse time with the ultra-pure water incleaning tank 5 from 10 minutes, 1 day, 3 days, to 7 days. Afterrinsing, the silicon wafer is dried, and the quantity of metalimpurities such as copper, iron or nickel, among deposited impurities,is measured by a total reflection X-ray spectrometer, the resultsthereof being shown in Table 1.

EXAMPLE 3

In the same cleaner as used in Example 1, a film module having achelating group is introduced, as ion absorption film module 20, betweena supply outlet to cleaning tank 5 and 0.1 μm particle eliminationmembrane filter 21 in branch piping 7 inside the cleaning machine,supplying cleaning tank 5 with ultra-pure water, all the ultra-purewater being filtered by module 20 before introduction into cleaning tank5.

First, cleaning with ozone ultra-pure water in cleaning tank 1 throughcleaning with dilute fluoric acid in cleaning tank 4 is performed upon asilicon wafer, prepared by a taking up method, the silicon wafer being 8inches in diameter (cz) and having an n-type crystal face (100) andresistivity of 8 to 12 Ω·cm. Next, the cleaning is performed by changingthe rinse time with the ultra-pure water in cleaning tank 5 from 10minutes, 1 day, 3 days, to 7 days. After rinsing, the silicon wafer isdried, and the quantity of metal impurities such as copper, iron ornickel, among the deposited impurities, is measured by a totalreflection X-ray spectrometer, the results thereof being shown in Table1.

Comparative Example 1

In the same cleaner as Example 1, ultra-pure water is supplied withoutintroducing an ion absorption module.

First, cleaning with ozone ultra-pure water in cleaning tank 1 throughcleaning with dilute fluoric acid in the cleaning tank 4 is performedupon a silicon wafer, prepared by a taking up method, of 8 inches indiameter (cz) and having an n-type crystal face (100) and a resistivityof 8 to 12 Ω·cm. Next, the cleaning is performed by changing the rinsetime with the ultra-pure water in cleaning tank 5 from 10 minutes, 1day, 3 days, to 7 days. After rinsing, the silicon wafer is dried, andthe quantity of metal impurities such as copper, iron or nickel, amongthe deposited impurities, is measured by a total reflection X-rayspectrometer, the results thereof being shown in Table 1.

Comparative Example 2

In the same cleaner as Example 1, an anion absorption film module isintroduced, as ion absorption film module 20, in branch piping 7supplying cleaning tank 5 with ultra-pure water but positioned outsidethe cleaning machine, all the ultra-pure water being filtered by module20 before introduction thereof into cleaning tank 5.

First, cleaning with ozone ultra-pure water in cleaning tank 1 throughcleaning with dilute fluoric acid in cleaning tank 4 is performed upon asilicon wafer, prepared by a taking up method of 8 inches in diameter(cz) and having an n-type crystal face (100) and a resistivity of 8 to12 Ω·cm. Next, the cleaning is performed by changing the rinse time withthe ultra-pure water in cleaning tank 5 from 10 minutes, 1 day, 3 days,to 7 days.

After rinsing, the silicon wafer is dried, and the quantity of metalimpurities such as copper, iron or nickel, among the depositedimpurities, is measured by a total reflection X-ray spectrometer, theresults thereof being shown in Table 1.

Comparative Example 3

In the same cleaner as Example 1, a cation absorption film module isintroduced, as ion absorption film module 20, in branch piping 7,supplying cleaning tank 5 with ultra-pure water, but outside thecleaning machine, all the ultra-pure water being filtered by module 20before introduction thereof into cleaning tank 5.

First, cleaning with ozone ultra-pure water in cleaning tank 1 throughcleaning with dilute fluoric acid in cleaning tank 4 is performed upon asilicon wafer, prepared by a taking up method, of 8 inches in diameter(cz) and having an n-type crystal face (100) and a resistivity of 8 to12 Ω·cm. Next, the cleaning is performed by changing the rinse time withthe ultra-pure water in cleaning tank 5 from 10 minutes, 1 day, 3 days,to 7 days. After rinsing, the silicon wafer is dried, and the quantityof metal impurities such as copper, iron or nickel, among the depositedimpurities, is measured by a total reflection X-ray spectrometer, theresults thereof being shown in Table 1.

Comparative Example 4

In the same cleaner as Example 1, a film module provided with achelating group is introduced, as ion absorption film module 20, inbranch piping 7 supplying cleaning tank 5 with ultra-pure water, butoutside the cleaning machine, all the ultra-pure water being filtered bymodule 20 before introduction thereof into cleaning tank 5.

First, cleaning with ozone ultra-pure water in cleaning tank 1 throughcleaning with dilute fluoric acid in cleaning tank 4 is performed upon asilicon wafer, prepared by a taking up method, of 8 inches in diameter(cz) and having an n-type crystal face (100) and a resistivity of 8 to12 Ω·cm. Next, the cleaning is performed by changing the rinse time withthe ultra-pure water in cleaning tank 5 from 10 minutes, 1 day, 3 days,to 7 days. After rinsing, the silicon wafer is dried, and the quantityof metal impurities such as copper, iron or nickel, among the depositedimpurities, is measured by a total reflection X-ray spectrometer, theresults thereof being shown in Table 1.

EXAMPLE 4

A mixing tank 8 is installed in cleaning tank 2, and mixing tank 8 issuitably supplied with the necessary chemicals from a weighing tank 10of fluoric acid containing surfactant and from a weighing tank 11 ofhydrogen peroxide, and when mixing is finished, the chemicals aretransported from mixing tank 8 to cleaning tank 2.

A mixing tank 9 is installed in cleaning tank 4, and mixing tank 9 issuitably supplied with the necessary chemicals from a weighing tank 12of fluoric acid, and when mixing is finished, the chemicals aretransported from mixing tank 9 to cleaning tank 4.

Cleaning tank 5 is supplied with ultra-pure water from ultra-pure waterpiping 7, the dissolved oxygen concentration of this ultra-pure waterbeing 2 μg/L and the dissolved hydrogen concentration being 1 mg/L.

An anion absorption film module is introduced, as ion absorption filmmodule 20, between a supply outlet to tank 5 and 0.1 μm particleelimination membrane filter 21 in branch piping 7 inside a cleaningmachine supplying cleaning tank 5 with ultra-pure water, all theultra-pure water being filtered by module 20 before introduction thereofinto cleaning tank 5.

First, cleaning with ozone ultra-pure water in cleaning tank 1 throughcleaning with dilute fluoric acid in cleaning tank 4 is performed upon asilicon wafer, prepared by a taking up method, of 8 inches in diameter(cz) and having an n-type crystal face (100) and a resistivity of 8 to12 Ω·cm. Next, the cleaning is performed by changing the rinse time withthe ultra-pure water in cleaning tank 5 from 10 minutes, 1 day, 3 days,to 7 days. After rinsing, the silicon wafer is dried, and the quantityof metal impurities such as copper, iron or nickel, among the depositedimpurities, is measured by a total reflection X-ray spectrometer, theresults thereof being shown in Table 2.

EXAMPLE 5

In the same cleaner as Example 4, a cation absorption film module isintroduced as ion absorption film module 20, between the supply outletto tank 5 and 0.1 μm particle elimination membrane filter 21 in branchpiping 7 inside the cleaning machine, supplying cleaning tank 5 withultra-pure water, all the ultra-pure water being filtered by module 20before introduction thereof into cleaning tank 5.

First, cleaning with ozone ultra-pure water in cleaning tank 1 throughcleaning with dilute fluoric acid in cleaning tank 4 is performed upon asilicon wafer, prepared by a taking up method, of 8 inches in diameter(cz) and having an n-type crystal face (100) and a resistivity of 8 to12 Ω·cm. Next, the cleaning is performed by changing the rinse time withthe ultra-pure water in cleaning tank 5 from 10 minutes, 1 day, 3 days,to 7 days. After rinsing, the silicon wafer is dried, and the quantityof metal impurities such as copper, iron or nickel, among the depositedimpurities, is measured by a total reflection X-ray spectrometer, theresults thereof being shown in Table 2.

EXAMPLE 6

In the same cleaner as Example 4, a film module having a chelating groupis introduced, as ion absorption film module 20, between a supply outletto tank 5 and 0.1 μm particle elimination membrane filter 21 in branchpiping 7 inside the cleaning machine, supplying cleaning tank 5 withultra-pure water, all the ultra-pure water being filtered by module 20before introduction thereof into cleaning tank 5.

First, cleaning with ozone ultra-pure water in cleaning tank 1 throughcleaning with dilute fluoric acid in cleaning tank 4 is performed upon asilicon wafer, prepared by a taking up method, of 8 inches in diameter(cz) and having an n-type crystal face (100) and a resistivity of 8 to12 Ω·cm. Next, the cleaning is performed by changing the rinse time withthe ultra-pure water in cleaning tank 5 from 10 minutes, 1 day, 3 days,to 7 days. After rinsing, the silicon wafer is dried, and the quantityof metal impurities such as copper, iron or nickel, among the depositedimpurities, is measured by a total reflection X-ray spectrometer, theresults thereof being shown in Table 2.

Comparative Example 5

In the same cleaner as Example 4, ultra-pure water is supplied withoutintroducing an ion absorption module.

First, cleaning with ozone ultra-pure water in cleaning tank 1 throughcleaning with dilute fluoric acid in cleaning tank 4 is performed upon asilicon wafer, prepared by a taking up method, of 8 inches in diameter(cz) and having an n-type crystal face (100) and a resistivity of 8 to12 Ω·cm. Next, the cleaning is performed by changing the rinse time withthe ultra-pure water in cleaning tank 5 from 10 minutes, 1 day, 3 days,to 7 days. After rinsing, the silicon wafer is dried, and the quantityof metal impurities such as copper, iron or nickel, among the depositedimpurities, is measured by a total reflection X-ray spectrometer, theresults thereof being shown in Table 2.

EXAMPLE 7

FIG. 3 shows an ambient temperature wet cleaning apparatus configuredfor performing a five-step cleaning process. Cleaning with ozoneultra-pure water is performed in cleaning tank 1, and megasonicirradiation cleaning is performed by adding surfactant to a fluoricacid-hydrogen peroxide mixture solution in cleaning tank 2. Cleaning isperformed with ozone ultra-pure water in cleaning tank 3, a dilutefluoric acid treatment in cleaning tank 4, and a final ultra-pure waterrinse in cleaning tank 5.

Cleaning tank 1 and cleaning tank 3 are supplied with ultra-pure waterfrom ultra-pure water piping 7, ozone generated by an ozone generator 6and ozone supplied from piping 13 are mixed and dissolved in theultra-pure water piping 7 and supplied into the cleaning tank as ozoneultra-pure water.

Mixing tank 8 is installed in cleaning tank 2, and mixing tank 8 issuitably supplied with the necessary chemicals from weighing tank 10 offluoric acid containing surfactant and from weighing tank 11 of hydrogenperoxide, and when mixing is finished, the chemicals are transportedfrom mixing tank 8 to cleaning tank 2.

Mixing tank 9 is installed in cleaning tank 4, and mixing tank 9 issuitably supplied with the necessary chemicals from weighing tank 12 offluoric acid, and when mixing is finished, the chemicals are transportedfrom mixing tank 9 to cleaning tank 4.

Cleaning tank 5 is supplied with ultra-pure water from ultra-pure waterpiping 7, the dissolved oxygen concentration of this ultra-pure waterbeing 2 μg/L.

An anion absorption film module is introduced, as ion absorption filmmodule 20, between a supply outlet to cleaning tank 5 and the 0.1 μmparticle elimination membrane filter in branch piping 7 inside acleaning machine, supplying cleaning tank 5 with the ultra-pure water,then a hydrogen solved film module 19 using polyolefin hollow yarn isintroduced.

Hydrogen gas is added so that the dissolved hydrogen concentration athydrogen solved film module 19 becomes 1 mg/L.

First, cleaning with ozone ultra-pure water in cleaning tank 1 throughcleaning with dilute fluoric acid in cleaning tank 4 is performed upon asilicon wafer, prepared by a taking up method, of 8 inches in diameter(cz) and having an n-type crystal face (100) and a resistivity of 8 to12 Ω·cm. Next, the cleaning is performed by changing the rinse time withthe ultra-pure water in cleaning tank 5 from 10 minutes, 1 day, 3 days,to 7 days. After rinsing, the silicon wafer is dried, and the quantityof metal impurities such as copper, iron or nickel, among the depositedimpurities, is measured by a total reflection X-ray spectrometer, theresults thereof being shown in Table 3.

EXAMPLE 8

In the same cleaner as Example 7, a cation absorption film module isintroduced, as ion absorption film module 20, then hydrogen solved filmmodule 19 using a polyolefin hollow yarn is introduced. Hydrogen gas isadded so that dissolved hydrogen concentration at hydrogen solved filmmodule 19 becomes 1 mg/L.

First, cleaning with ozone ultra-pure water in cleaning tank 1 throughcleaning with dilute fluoric acid in cleaning tank 4 is performed upon asilicon wafer, prepared by a taking up method, of 8 inches in diameter(cz) and having an n-type crystal face (100) and a resistivity of 8 to12 Ω·cm. Next, the cleaning is performed by changing the rinse time withthe ultra-pure water in cleaning tank 5 from 10 minutes, 1 day, 3 days,to 7 days. After rinsing, the silicon wafer is dried, and the quantityof metal impurities such as copper, iron or nickel, among the depositedimpurities, is measured by a total reflection X-ray spectrometer, theresults thereof being shown in Table 3.

EXAMPLE 9

In the same cleaner as Example 1, a film module having chelating groupis introduced, as ion absorption film module 20, then a hydrogen solvedfilm module 19 using a polyolefin hollow yarn is introduced. Hydrogengas is added so that the dissolved hydrogen concentration at hydrogensolved film module 19 becomes 1 mg/L.

First, cleaning with ozone ultra-pure water in cleaning tank 1 throughcleaning with dilute fluoric acid in cleaning tank 4 is performed upon asilicon wafer, prepared by a taking up method, of 8 inches in diameter(cz) and having an n-type crystal face (100) and a resistivity of 8 to12 Ω·cm. Next, the cleaning is performed by changing the rinse time withthe ultra-pure water in cleaning tank 5 from 10 minutes, 1 day, 3 days,to 7 days. After rinsing, the silicon wafer is dried, and the quantityof metal impurities such as copper, iron or nickel, among the depositedimpurities, is measured by a total reflection X-ray spectrometer, theresults thereof being shown in Table 3.

Comparative Example 6

In the same cleaner as Example 7, a hydrogen solved film module 19 usinga polyolefin hollow yarn is introduced, without installing an ionabsorption module 20 in piping 7 supplying cleaning tank 5. Hydrogen gasis added so that the dissolved hydrogen concentration at the hydrogensolved film module 19 becomes 1 mg/L.

First, cleaning with ozone ultra-pure water in cleaning tank 1 throughcleaning with dilute fluoric acid in cleaning tank 4 is performed upon asilicon wafer, prepared by a taking up method, of 8 inches in diameter(cz) and having an n-type crystal face (100) and a resistivity of 8 to12 Ω·cm. Next, the cleaning is performed by changing the rinse time withthe ultra-pure water in cleaning tank 5 from 10 minutes, 1 day, 3 days,to 7 days. After rinsing, the silicon wafer is dried, and the quantityof metal impurities such as copper, iron or nickel, among the depositedimpurities, is measured by a total reflection X-ray spectrometer, theresults thereof being shown in Table 3.

EXAMPLE 10

FIG. 4 shows an ambient temperature wet cleaning apparatus forfacilitating a five-step wet cleaning process. Cleaning with ozoneultra-pure water is performed in cleaning tank 1 and megasonicirradiation cleaning is performed by adding a surfactant to a fluoricacid-hydrogen peroxide mixture solution in cleaning tank 2.

Cleaning is performed with ozone ultra-pure water in cleaning tank 3, adilute fluoric acid treatment in cleaning tank 4, and a final ultra-purewater rinse in cleaning tank 5.

Cleaning tank 1 and cleaning tank 3 are supplied with ultra-pure waterfrom ultra-pure water piping 7. Ozone generated by ozone generator 6 andozone supplied from piping 13 are mixed and dissolved in the ultra-purewater within piping 7 and supplied into cleaning tank 5 as ozoneultra-pure water.

Mixing tank 8 is installed in cleaning tank 2, and mixing tank 8 issuitably supplied with the necessary chemicals from weighing tank 10 offluoric acid containing a surfactant and from weighing tank 11 ofhydrogen peroxide, and when mixing is finished, the chemicals aretransported from mixing tank 8 to cleaning tank 2.

Mixing tank 9 is installed in cleaning tank 4, and mixing tank 9 issuitably supplied with the necessary chemicals from weighing tank 12 offluoric acid, and when mixing is finished, the chemicals are transportedfrom mixing tank 9 to cleaning tank 4.

Cleaning tank 5 is supplied with ultra-pure water from ultra-pure waterpiping 7, the dissolved oxygen concentration of this ultra-pure waterbeing 2 μg/L.

A cation absorption film module 20 is introduced, between a supplyoutlet to tank 5 and 0.1 μm particle elimination membrane filter 21 inbranch piping 7 inside a cleaning machine, supplying cleaning tank 5with ultra-pure water, then anion absorption film module 21 isintroduced, all the ultra-pure water being filtered by modules 20,21before being introduced into cleaning tank 5.

An MOS diode of gate oxide film thickness (4.5 nm) is prepared, usingthis cleaning machine. A dielectric breakdown characteristic test of theMOS diode is performed on a device having a device area of 1×10⁻⁴ cm²and a control current value of 1×10⁻⁴ A to investigate the average valueof dielectric breakdown voltage of the device (device number 100), theresults thereof being shown in Table 4.

EXAMPLE 11

In the same cleaner as Example 10, a chelate absorption film module 20is introduced, between a supply outlet to tank 5 and 0.1 μm particleelimination membrane filter 21 in branch piping 7 inside a cleaningmachine, supplying cleaning tank 5 with ultra-pure water and thenintroducing anion absorption film module 21, all the ultra-pure waterbeing filtered by modules 21 before being introduced into cleaning tank5.

An MOS diode of gate oxide film thickness (4.5 nm) is prepared, usingthis cleaning machine. A dielectric breakdown characteristic test of theMOS diode is performed on a device having a device area of 1×10⁻⁴ cm²and a control current value of 1×10 ⁻⁴ A to investigate the averagevalue of dielectric breakdown voltage of the device (device number 100),the results thereof being shown in Table 4.

EXAMPLE 12

In the same cleaner as Example 10, a anion absorption film module 20 isintroduced, between a supply outlet to tank 5 and 0.1 μm particleelimination membrane filter 22 in branch piping 7 inside a cleaningmachine, supplying cleaning tank 5 with ultrapure water and thenintroducing a chelate absorption film module 21, all the ultra-purewater being filtered by modules 20,21 before being introduced intocleaning tank 5.

An MOS diode of gate oxide film thickness (4.5 nm) is prepared, usingthis cleaning machine. A dielectric breakdown characteristic test of theMOS diode is performed on a device having a device area of 1×10⁻⁴ cm²and a control current value of 1×10 ⁻⁴ A to investigate the averagevalue of dielectric breakdown voltage of the device (device number 100),the results thereof being shown in Table 4.

EXAMPLE 13

In the same cleaner as Example 10, a cation absorption film module 20 isintroduced, between a supply outlet to tank 5 and 0.1 μm particleelimination membrane filter 22 in branch piping 7 inside a cleaningmachine, supplying cleaning tank 5 with ultra-pure water and thenintroducing a chelate absorption film module 21, all the ultra-purewater being filtered by modules 20,21 before being introduced intocleaning tank 5.

An MOS diode of gate oxide film thickness (4.5 nm) is prepared, usingthis cleaning machine. A dielectric breakdown characteristic test of theMOS diode is performed on a device having a device area of 1×10⁻⁴ cm²and a control current value of 1×10⁻⁴ A to investigate the average valueof dielectric breakdown voltage of the device (device number 100), theresults thereof being shown in Table 4.

EXAMPLE 14

In the same cleaner as Example 10, only an anion absorption film module20 is introduced, between a supply outlet to tank 1 and the 0.1 μmparticle elimination membrane filter 22 in branch piping 7 inside acleaning machine, supplying cleaning tank 5 with ultra-pure water, andall the ultra-pure water being filtered by these modules before beingintroduced into cleaning tank 5.

An MOS diode of gate oxide film thickness (4.5 nm) is prepared, usingthis cleaning machine. The dielectric breakdown characteristic test ofthe prepared MOS diode (the MOS diode having a device area of 1×10⁻⁴cm², a control current value of 1×10⁻⁴ A) to investigate the averagevalue of dielectric breakdown voltage of the device (device number 100),the results thereof being shown in Table 4.

EXAMPLE 15

FIG. 5 shows an ambient temperature wet cleaning apparatus forfacilitating a five-step cleaning process. Cleaning with ozoneultra-pure water is performed in cleaning tank 1, and megasonicirradiation cleaning is performed by adding a surfactant to a fluoricacid-hydrogen peroxide mixture solution in cleaning tank 2.

Cleaning is performed with ozone ultra-pure water in cleaning tank 3, adilute fluoric acid treatment in cleaning tank 4, and a final ultra-purewater rinse in cleaning tank 5.

Cleaning tank 1 and cleaning tank 3 are supplied with ultra-pure waterfrom ultra-pure water piping 7. Ozone generated by ozone generator 6 andozone supplied from piping 13 are mixed and dissolved in the ultra-purewater within piping 7 and supplied into cleaning tank 5 as ozoneultra-pure water.

Mixing tank 8 is installed in cleaning tank 2, and mixing tank 8 issuitably supplied with necessary chemicals from weighing tank 10 offluoric acid containing the surfactant and from weighing tank 11 ofhydrogen peroxide, and when mixing is finished, the chemicals aretransported from mixing tank 8 to cleaning tank 2.

Mixing tank 9 is installed in cleaning tank 4, and mixing tank 9 issuitably supplied with the necessary chemicals from weighing tank 12 offluoric acid, and when mixing is finished, the chemicals are transportedfrom mixing tank 9 to cleaning tank 4.

Cleaning tank 5 is supplied with ultra-pure water from ultra-pure waterpiping 7, the dissolved oxygen concentration of this ultra-pure waterbeing 2 μg/L.

A cation absorption film module 20 is introduced, between a supplyoutlet to tank 5 and 0.1 μm particle elimination membrane filter 21 in abranch piping 7 inside a cleaning machine, supplying cleaning tank 5with ultra-pure water, then a film module 21 provided with a chelatinggroup and further an anion absorption film module 22 are introduced, allthe ultra-pure water being filtered by these modules before beingintroduced into cleaning tank 5.

An MOS diode of gate oxide film thickness (3.5 nm) is prepared, usingthis cleaning machine. A dielectric breakdown characteristic test of theMOS diode is performed on a device having a device area of 1×10⁻⁴ cm²and a control current value of 1×10⁻⁴ A to investigate the average valueof dielectric breakdown voltage of the device (device number 100), theresults thereof being shown in Table 5.

EXAMPLE 16

In the same cleaner as Example 14, a film module 20 provided with achelating group is introduced, between a supply outlet to tank 5 and 0.1μm particle elimination membrane filter 21 in branch piping 7 inside acleaning machine, supplying cleaning tank 5 with ultra-pure water, thena cation absorption film module 21 and further an anion absorption filmmodule 22 are introduced, all the ultra-pure water being filtered bythese modules before being introduced into cleaning tank 5.

An MOS diode of gate oxide film thickness (3.5 nm) is prepared, usingthis cleaning machine.

A dielectric breakdown characteristic test of the MOS diode is performedon a device having a device area of 1×10⁻⁴ cm² and a control currentvalue of 1×10⁻⁴ A to investigate the average value of the dielectricbreakdown voltage of the device (device number 100), the results thereofbeing shown in Table 5.

EXAMPLE 17

In the same cleaner as Example 14, a film module 20 provided with achelating group is introduced, between a supply outlet to thank 5 and0.1 μparticle elimination membrane filter 21 in branch piping 7 inside acleaning machine, supplying cleaning tank 5 with ultra-pure water, thenan anion absorption film module 21 and further a cation absorption filmmodule 22 are introduced, all the ultra-pure water is filtered by thesemodules before being introduced into cleaning tank 5.

An MOS diode of gate oxide film thickness (3.5 nm) is prepared, usingthis cleaning machine. The dielectric breakdown characteristic test ofthe MOS diode is performed on a device having a device area of 1×10⁻⁴cm² and a control current value of 1×10⁻⁴ A to investigate the averagevalue of the dielectric breakdown voltage of the device (device number100), the results thereof being shown in Table 5.

EXAMPLE 18

In the same cleaner as Example 14, a cation absorption film module 20 isintroduced, between a supply outlet to tank 5 and 0.1 μm particleelimination membrane filter 21 in branch piping 7 inside a cleaningmachine, supplying cleaning tank 5 with ultra-pure water, then an anionabsorption film module 21 and further a film module 22 provided withchelating group are introduced the ultra-pure water being filtered bythese modules before being introduced into cleaning tank 5.

An MOS diode of gate oxide film thickness (3.5 nm) is prepared, usingthis cleaning machine. The dielectric breakdown characteristic test ofthe MOS diode is performed on a device having a device area of 1×10⁻⁴cm² and a control current value of 1×10⁻⁴ A to investigate the averagevalue of the dielectric breakdown voltage of the device (device number100), the results thereof being shown in Table 5.

EXAMPLE 19

In the same cleaner as Example 10, a anion absorption film module 20 isintroduced, between a supply outlet to tank 5 and 0.1 μm particleelimination membrane filter 21 in branch piping 7 inside a cleaningmachine, supplying cleaning tank 5 with ultra-pure water, then a cationabsorption film module 22 is introduced, all the ultra-pure water beingfiltered by these modules before being introduced into cleaning tank 5.

An MOS diode of gate oxide film thickness (4.5 nm) is prepared, usingthis cleaning machine.

A dielectric breakdown characteristic test of the MOS diode is performedon a device having a device area of 1×10⁻⁴ cm² and a control currentvalue of 1×10⁻⁴ A to investigate the average value of the dielectricbreakdown voltage of the device (device number 100), the results thereofbeing shown in Table 5.

TABLE 1 Amount of metal deposited onto silicon wafer (unit: ×10⁹atoms/cm²) Copper Iron Nickel Before Rinse Example 1 quantificationquantification quantification lower limit or lower limit or lower limitor less less less Example 2 quantification quantification quantificationlower limit or lower limit or lower limit or less less less Example 3quantification quantification quantification lower limit or lower limitor lower limit or less less less Comparison 1 quantificationquantification quantification lower limit or lower limit or lower limitor less less less Comparison 2 quantification quantificationquantification lower limit or lower limit or lower limit or less lessless Comparison 3 quantification quantification quantification lowerlimit or lower limit or lower limit or less less less Comparison 4quantification quantification quantification lower limit or lower limitor lower limit or less less less 10 minute rinse Example 1quantification quantification quantification lower limit or lower limitor lower limit or less less less Example 2 quantification quantificationquantification lower limit or lower limit or lower limit or less lessless Example 3 quantification quantification quantification lower limitor lower limit or lower limit or less less less Comparison 1quantification quantification quantification lower limit or lower limitor lower limit or less less less Comparison 2 quantificationquantification quantification lower limit or lower limit or lower limitor less less less Comparison 3 quantification quantificationquantification lower limit or lower limit or lower limit or less lessless Comparison 4 quantification quantification quantification lowerlimit or lower limit or lower limit or less less less 1 day rinseExample 1 quantification quantification quantification lower limit orlower limit or lower limit or less less less Example 2 quantificationquantification quantification lower limit or lower limit or lower limitor less less less Example 3 quantification quantification quantificationlower limit or lower limit or lower limit or less less less Comparison 14.1 9.7 quantification lower limit or less Comparison 2 quantificationquantification quantification lower limit or lower limit or lower limitor less less less Comparison 3 quantification quantificationquantification lower limit or lower limit or lower limit or less lessless Comparison 4 quantification quantification quantification lowerlimit or lower limit or lower limit or less less less 3 day rinseExample 1 quantification quantification quantification lower limit orlower limit or lower limit or less less less Example 2 quantificationquantification quantification lower limit or lower limit or lower limitor less less less Example 3 quantification quantification quantificationlower limit or lower limit or lower limit or less less less Comparison 112 40 4.9 Comparison 2 quantification 5.7 quantification lower limit orlower limit or less less Comparison 3 2.5 11 quantification lower limitor less Comparison 4 quantification 3.8 quantification lower limit orlower limit or less less 7 day rinse Example 1 quantification 5.8quantification lower limit or lower limit or less less Example 2 2.9 3.2quantification lower limit or less Example 3 3.3 3.5 quantificationlower limit or less Comparison 1 30 89 12 Comparison 2 5.8 18quantification lower limit or less Comparison 3 8.3 20 3.0 Comparison 46 11 4.3

Copper quantification lower limit: 1.8×10⁹ atoms/cm²

Iron quantification lower limit: 3.2×10⁹ atoms/cm²

Nickel quantification lower limit: 2.0×10⁹ atoms/cm²

TABLE 2 Amount of metal deposited onto silicon wafer (unit: ×10⁹atoms/cm²) Copper Iron Nickel Before Rinse Example 4 quantificationquantification quantification lower limit or lower limit or lower limitor less less less Example 5 quantification quantification quantificationlower limit or lower limit or lower limit or less less less Example 6quantification quantification quantification lower limit or lower limitor lower limit or less less less Comparison 5 quantificationquantification quantification lower limit or lower limit or lower limitor less less less 10 minute rinse Example 4 quantificationquantification quantification lower limit or lower limit or lower limitor less less less Example 5 quantification quantification quantificationlower limit or lower limit or lower limit or less less less Example 6quantification quantification quantification lower limit or lower limitor lower limit or less less less Comparison 5 quantificationquantification quantification lower limit or lower limit or lower limitor less less less 1 day rinse Example 4 quantification quantificationquantification lower limit or lower limit or lower limit or less lessless Example 5 quantification quantification quantification lower limitor lower limit or lower limit or less less less Example 6 quantificationquantification quantification lower limit or lower limit or lower limitor less less less Comparison 5 20 6.4 quantification lower limit or less3 day rinse Example 4 quantification quantification quantification lowerlimit or lower limit or lower limit or less less less Example 5quantification quantification quantification lower limit or lower limitor lower limit or less less less Example 6 quantification quantificationquantification lower limit or lower limit or lower limit or less lessless Comparison 5 32 10.5 2.7 7 day rinse Example 4 quantificationquantification quantification lower limit or lower limit or lower limitor less less less Example 5 3.1 3.2 quantification lower limit or lessExample 6 quantification quantification quantification lower limit orlower limit or lower limit or less less less Comparison 5 74 21 6.3

Copper quantification lower limit: 1.8×10⁹ atoms/cm²

Iron quantification lower limit: 3.2×10⁹ atoms/cm²

Nickel quantification lower limit: 2.0×10⁹ atoms/cm²

TABLE 3 Amount of metal deposited onto silicon wafer (unit: ×10⁹atoms/cm²) Copper Iron Nickel Before rinse Example 7 quantificationquantification quantification lower limit or lower limit or lower limitor less less less Example 8 quantification quantification quantificationlower limit or lower limit or lower limit or less less less Example 9quantification quantification quantification lower limit or lower limitor lower limit or less less less Comparison 6 quantificationquantification quantification lower limit or lower limit or lower limitor less less less 10 minute rinse Example 7 quantificationquantification quantification lower limit or lower limit or lower limitor less less less Example 8 quantification quantification quantificationlower limit or lower limit or lower limit or less less less Example 9quantification quantification quantification lower limit or lower limitor lower limit or less less less Comparison 6 quantificationquantification quantification lower limit or lower limit or lower limitor less less less 1 day rinse Example 7 quantification quantificationquantification lower limit or lower limit or lower limit or less lessless Example 8 quantification quantification quantification lower limitor lower limit or lower limit or less less less Example 9 quantificationquantification quantification lower limit or lower limit or lower limitor less less less Comparison 6  3 9.1 quantification lower limit or less3 day rinse Example 7 quantification 3.2 quantification lower limit orlower limit or less less Example 8 quantification 3.2 quantificationlower limit or lower limit or less less Example 9 quantificationquantification quantification lower limit or lower limit or lower limitor less less less Comparison 6 10 33 4.9 7 days rinse Example 7quantification 3.2 quantification lower limit or lower limit or lessless Example 8 quantification 3.2 quantification lower limit or lowerlimit or less less Example 9 quantification quantificationquantification lower limit or lower limit or lower limit or less lessless Comparison 6 10 33 4.9

Copper quantification lower limit: 1.8×10⁹ atoms/cm²

Iron quantification lower limit: 3.2×10⁹ atoms/cm²

Nickel quantification lower limit: 2.0×10⁹ atoms/cm²

TABLE 4 Dielectric breakdown characteristic test of MOS diode (Averageof 100 devices) (Unit: MV/cm) Example Example Example Example Example 1011 12 13 14 Dielectric 12.0 12.2 12.3 12.2 10.4 breakdown electric field

Gate oxide film thickness: 45 Å

Device area: 1×10⁻⁴ cm²

Control current value: 1×10⁻⁴ A

TABLE 5 Dielectric breakdown characteristic test cf MOS diode (Averageof 100 devices) (Unit : MV/cm) Example Example Example Example Example15 16 17 18 19 Dielectric 11.5 11.3 11.7 11.5 9.5 breakdown electricfield

Gate oxide film thickness: 45 Å

Device area: 1×10⁻⁴ cm²

Control current value: 1×10⁻⁴ A

Possible Industrial Applications

The cleaning process of the present invention can be used to removeclustered metal (silica, clustered with organic matter lowering electriccharge) that can not be removed with conventional ultra-pure waterproduction apparatus and can be used to reduce the amount of metaldeposition onto the substrate during wet processing, especially duringthe rinse phase.

As the amount of metal deposition onto the substrate can be reduced,reduction of device defect (fail bit) due to wet processing is expected.

While this invention has been described as having a preferred design,the present invention can be further modified within the spirit andscope of this disclosure. This application is therefore intended tocover any variations, uses, or adaptations of the invention using itsgeneral principles. Further, this application is intended to cover suchdepartures from the present disclosure as come within known or customarypractice in the art to which this invention pertains and which fallwithin the limits of the appended claims.

What is claimed is:
 1. A wet cleaning apparatus for rinsing withultra-pure water as a rinse liquid comprising: a piping for supplyingtherethrough ultra-pure water to a rinse location inside the apparatus,the rinse location being a point of use of the ultra-pure water; atleast one module filled with porous film in which polymer chains havingat least one of an anion exchange group, a cation exchange group, and achelating group are held in the middle of the piping positioned insidethe apparatus; and a means for adding hydrogen gas to said rinse liquidsaid means for adding being an introduction module associated with thepiping.
 2. The wet cleaning apparatus of claim 1, wherein said hydrogengas adding means is provided one of upstream and downstream said module.3. The wet cleaning apparatus of claim 1, wherein said hydrogen gasadding means is provided downstream said module.
 4. The wet cleaningapparatus on claim 1, having a combination of any two or more modulesfilled with at least one of a polymer-chain-holding porous film havingan anion exchange group, a polymer-chain-holding porous film having acation exchange group and a polymer-chain-holding porous film having achelating group is provided.